I’ve seen them on other people’s bikes both when riding and in the car and I don’t think they add to visibility as much as I expected them to.
2 x big LED lights (I use Moon Shields). One flashing, on constant. Respro ankle bands.
This is my approach. A couple of decent LED lights – they don’t need to burn out the retinas, but the combination of one static and one flashing attracts attention without messing with speed/distance perception.
The movement of reflective ankle bands helps identify as a cyclist and works side on as well.
Tyres with reflective sidewalls are worth seeking out (though you do actually need to clean them occasionally). Low/no marginal cost, always on, mark as a bike, side visibility.
Frankly though, on unlit lanes the danger is someone simply driving like a twunt relying on headlights coming towards them.